The correct balance of soil nutrients is the key to improving grassland nutrition but can be difficult to achieve. Many farms could benefit from adopting a multi-vitamin approach to this challenge.

It is well-documented that grass is the cheapest feed for ruminant livestock with energy from this source costing approximately 25 per cent that from concentrates.
As a result, livestock farmers will know achieving good yields of highly digestible, high quality forage is critical to maximising herd performance. Yet getting the best from the crop depends on meeting all of its nutritional requirements.
This is a point emphasised by Jim Holt, a fertiliser specialist with manufacturer and distributor J. and H. Bunn who says: “The key to capitalising on the potential of grass is to treat it just like any other high value crop, which is often easier said than done.

The starting point is to have soils tested regularly to pinpoint any nutritional deficiencies

Jim Holt

“The general lack of good agronomy advice available to grassland enterprises throughout the UK means even experienced farmers who recognise the performance of their swards is sub-optimal, may struggle to pinpoint the exact cause. The starting point is to have soils tested regularly to pinpoint any nutritional deficiencies.”
He said this testing is currently carried out on less than half of livestock farms despite grass having a high demand for all nutrients, particularly nitrogen, sodium and potash, and especially when it is intensively managed for silage or hay.
“The inter-relationship of potash, sulphur, magnesium, sodium and nitrogen is complex, but has a significant impact on sward composition, crop performance, quality, palatability and animal health.
“Therefore, it is essential to ensure these are available in sufficient quantities. Applying them together minimises the risk of an imbalance being created.”

Optimise

Mr Holt says adopting a multi-vitamin approach to grassland nutrition could help many grassland farmers to maximise the performance of their swards and optimise livestock performance.
“Applying this approach in cases involving poor grassland performance can visibly improve appearance, performance, yield and quality while also improving utilisation of nitrogen fertilisers.”
“For example, tests from a farm I worked with last year showed the soil, particularly the silage ground, was deficient in potash.
“This led me to recommend an application of a naturally occurring mineral fertiliser, which resulted in significant improvements in both the appearance and quality of the grassland.”
According to the fertiliser company, K+S UK and Eire, potash deficiency is common on UK livestock farms, with 45 per cent of soils falling below the target index needed to achieve maximum grass yield.
Jerry McHoul, from K+S, says this occurs because the nutrient contribution from organic manures is often over-estimated. Even on highly-intensive, well-managed farms, there is a danger the potash requirement will not be fully met by organic manures alone.

Supplement

He says the negative balance will eventually deplete soil fertility, so supplementation with mineral fertilisers is necessary to replace the nutrients leaving the farm in the form of meat and milk, and through leaching.
“Taking two to three cuts from lower-yielding areas producing a net yield of 6.5t DM/ha could remove 175kg/ha of potash, 50 kg/ha of phosphate, 20kg/ha of magnesium and 38kg/ha of sulphur,” says Mr McHoul.
“Taking more cuts from higher-yielding areas producing a net yield of 11.0t DM/ha will increase these figures to 330 kg/ha potash, 110 kg/ha phosphate, 80 kg/ha magnesium and 75 kg/ha sulphur.”
He says a minimum of 2.5 per cent potassium content is required in grass dry matter to prevent yield and quality losses, but the amount removed from the field is often ignored, even though this is higher than all other nutrients, including nitrogen.
“The depletion of potash in such soils can therefore be rapid and dramatic unless a sufficient quantity is replaced.”

Research results

Independent UK trials have found grassland treated with a naturally occurring mineral fertiliser, (Magnesia-Kainit) out-yielded muriate of potash by more than 10 per cent, with improvements of up to 12 per cent in second-cut silage production.
Where the product was used, its sodium content means grass is generally ‘sweeter’ and more palatable to cows, which will improve dry-matter intakes.
Research on seven UK farms, with a total of 2,000 cows, showed these cows preferred to graze in areas which had been treated with Magnesia-Kainit, rather than NPK fertiliser.